Step 1:

Use a Vernier caliper (slide gauge) to measure the dimensions of the gears, chuck, motor and other components

The dimensions I got for mine are show

Step 2: Step 2 - the Drive Shaft

The drill I used had a drive shaft attached to a kind of head, this had an odd profile so I drew around it with and then scanned it into solid works. Once in solid works I used sketch points and spline tool to draw round the outline. After this I saved it as an SLMD so I could use it on the CNC machine

Step 3: Step 3 - Cutting Part

To cut the odd shape for the head I used a CNC machine and the SLMD file

The other parts to hold the motor and the gears were made using a metal lathe